Objective: The overall aim of the proposed research is to study the various metabolic activation and inactivation steps involved in the carcinogenesis by chemicals in general and by aromatic amines and amides in particular. It is known that N-hydroxylation of aromatic amines and amides is an activation step whereas ring-hydroxylation is an inactivation step. Similarly, oxidative dealkylation of dialkylnitrosamines and epoxidation of hydrocarbons are also shown to be activation processes. All of these metabolic steps are mediated via cytochrome P-450 present in the endoplasmic reticulum of liver and several other tissues of various animals. It is very important to know whether activation and inactivation processes are mediated via the same cytochrome P-450. Approach: It is proposed to solubilize these microsomal P-450 cytochrome by ionic or non-ionic detergents. Ion exchange or affinity column chromatography will be used for purification of these proteins. Immunological techniques will also be used for study of these proteins. Separated P-450 cytochromes will be reconstituted for oxidation study of various carcinogens. Role of cytochrome b5 and other flavoproteins present in the endoplasmic reticulum will also be investigated in oxidation of carcinogens.